1. Field of the Invention
The instant disclosure relates to a power supply; in particular, to an intelligent pulse control circuit used for a power supply.
2. Description of Related Art
Please refer to FIG. 1 showing a system block diagram of a conventional power supply. The conventional power supply 1 comprises a rectifier/filter circuit 11, a power factor correction stage 12, a pulse width modulation stage 13 and a standby output stage 14. When the power is turned on, the main output voltage Vo (+12V/+5V/+3.3/−12V for example) of the power supply 1 is provided to the load for operation. In standby status, the standby output stage 14 outputs a standby voltage Vo′.
Performance convert consumption would happen during the process of providing voltage to the load. Accordingly, every country has developed rules or criterion to restrict the problem of energy waste due to the performance convert consumption. The 80 PLUS® program developed by Ecos Consulting and the ENERGY STAR® program developed by US Environmental Protection Agency are the most widely used criterion. The 80 PLUS® program is a voluntary certification program by Ecos Consulting representing public utilities and energy saving organizations in Unites States. It certifies power supplies for computers and servers that have more than 80% energy efficiency at 20%, 50% and 100% of rated load in AC/DC conversion. In the year 2008, standards revised to add Bronze, Silver, and Gold higher efficiency level certifications of 80 PLUS® were provided. Ecos Consulting further added a specification for Platinum efficiency level in October 2009, and a Titanium certification in August 2011, wherein the Titanium specification defines more than 90% energy efficiency at 10% loading. It can be seen that power conversion efficiency has become the most important evaluation index. As for the ENERGY STAR® of the United States, the latest version 6.0, released by October 2013, points out the efficiency about 81% to 84% at 10% loading. However, in this very light load condition, the regular power loss (comprising switching loss of the semiconductor power switch, iron loss of the magnetic element, copper loss, and so on) is the majority of the total power loss. This is the main reason why the efficiency of the power supply cannot be increased in very light load.